Question

Isotones are the nuclides having:

• A. same mass numbers
• B. same atomic numbers
• C. same neutron number, but different atomic number
• D. different neutron number, and different mass number

Hint:

Remember the definitions: Isotopes have the same atomic number (\( Z \)), isobars have the same mass number (\( A \)), and isotones have the same neutron number (\( N = A - Z \)).

Answer 1

The Correct Option is C

Step 1: Define Isotones

Isotones are nuclides (atomic nuclei) that have the same number of neutrons but different numbers of protons (hence, different atomic numbers).

The atomic number (Z) represents the number of protons, while the mass number (A) is the total number of nucleons (protons + neutrons). The neutron number (N) is given by:

N = A − Z

Step 2: Evaluate the given options

• (A) Identical mass numbers: Nuclides with the same mass number (A) are called isobars (e.g., ¹⁴C and ¹⁴N). This does not define isotones.
• (B) Identical atomic numbers: Nuclides with the same atomic number (Z) are called isotopes (e.g., ¹²C and ¹⁴C). This does not define isotones.
• (C) Identical neutron number but different atomic numbers: This correctly defines isotones. Example: ¹⁴C (Z = 6, N = 8) and ¹⁵N (Z = 7, N = 8) have the same neutron number but different atomic numbers.
• (D) Different neutron and mass numbers: This does not represent isotones, since isotones must have the same neutron number.

Step 3: Final Conclusion

Isotones are characterized by an identical neutron number (N) and different atomic numbers (Z). Therefore, the correct option is:

Option (C)